1. Field of the Invention
The present invention relates to communication between a mobile communication network for a personal digital cellular telecommunication system (PDC) etc. and a TCP/IP (Transmission Control Protocol/Internet Protocol) communication network and, more particularly, to a method of transmission from a TCP/IP communication network to a mobile communication network for conducting transmission from a TCP/IP communication network to a mobile communication terminal accommodated in a mobile communication network for a personal digital cellular telecommunication system etc. (reception at the mobile communication terminal side) and a transmission and reception system therefor.
2. Description of the Related Art
Conventionally proposed is a technique of transferring data from a terminal (personal computer) and the like accommodated in a TCP/IP communication network (intranet, Internet, extranet) to a non-TCP/IP communication network, for example, the mobile communication terminal accommodated in a mobile communication network for a personal digital cellular telecommunication system (PDC) (e.g. “Method and System for Enabling Mobile Station to Participate in Data Communication” recited in Japanese Patent Laying-Open (Kokai) No. Heisei 11-27290).
Such a mobile communication terminal in a personal digital cellular telecommunication system conducts communication with a TCP/IP communication network through this mobile communication network. In this case, transmission from a mobile communication terminal to an Internet service provider is possible, while transmission using an IP packet from an Internet user (a terminal accommodated in the TCP/IP communication network) to a mobile communication terminal through an Internet service provider (reception at the mobile communication terminal side) is not possible in some cases.
FIG. 5 is a block diagram showing a structure of a conventional mobile communication system and FIG. 6 is a block diagram showing a structure of main components of a provider connection interworking function device for establishing Internet connection in the conventional mobile communication system. FIG. 7 is a diagram showing a sequence at the time of Internet connection in the conventional mobile communication system (transmission from a mobile communication terminal).
In FIG. 5, a data terminal (DTE) 1 such as a general-purpose small-sized computer (PC) conducts transmission to a terminal (e.g. personal computer) accommodated in the Internet (AT command (ATD). In response to this transmission, a data communication adapter (MS-ADP) 2, a mobile communication terminal (MS) 3, a radio base station (BTS) 4, a radio base station control device (BSC) 5 and a mobile communication switching system (MSC) 6 (calling processing device (CP) 6c/time-division switch (TDNW) 6a) are sequentially connected through a line by setup. At the mobile communication switching system 6, by the processing by the calling processing device 6c/the time-division switch 6a, a seizing signal (SEZ) is sent out to a provider connection interworking function device (PRV-IWF) 6b. 
The provider connection interworking function device 6b returns an acknowledge (ACK) in response to the seizing signal (SEZ) to the mobile communication switching system 6. The mobile communication switching system 6 sets a radio-side path. The data communication adapter 2 and the provider connection interworking function device 6b set an automatic retransmission request (ARQ).
The provider connection interworking function device 6b returns an answer (ANS) to the mobile communication switching system 6. The mobile communication switching system 6 sets a network-side path. The data terminal 1 sends an Internet protocol/transmission control protocol/synchronizing signal (IP+TCP(SYN)) to an access server (ACC-SER) 7 in an Internet service provider (ISP) 8. The access server 7 sends out the Internet protocol/transmission control protocol/synchronizing signal (IP+TCP (SYN)) to an Internet 9. Thereafter, between the data terminal 1 and a terminal not shown which is accommodated in the Internet 9, HTML data transmission etc. is conducted by TCP/IP link open.
In FIG. 6, at the provider connection interworking function device 6b, terminating processing circuits (ARQ-RX and ARQ-TX) 10a and 10b conduct terminating processing of an error control protocol on the side of a radio line. Asynchronous terminating processing circuits (ASYNC-RX and ASYNC-TX) 11a and 11b conduct terminating processing with respect to communication over a serial asynchronous line with the access server 7 on the side of the Internet service provider 8.
In this operation, the calling processing device 6c of the mobile communication switching system 6 controls the time-division switch 6a to set a user data transfer channel and a control channel with the radio base station control device 5. Also, an approach link is set between the radio base station (BTS) 4 and the radio base station control device (BSC) 5.
As described in the foregoing, the above conventional art fails to enable an Internet user (terminal) to conduct transmission using an IP packet to a mobile communication terminal (reception at the mobile communication terminal side) through an Internet service provider, which accordingly makes, for example, HTML data transmission impossible and causes inconvenience in use.